by Leah Messinger / The Guardian A protester at a public hearing before the South Coast Air Quality Management District in southern California. The Aliso Canyon leak has spewed 80,000 metric tons of methane since October, displacing thousands. Now experts say smaller leaks across the US pose a greater threat. Photograph: David McNew/Getty Images When Stephen Conley, an atmospheric scientist and pilot, saw an emissions indicator skyrocket in his Mooney TLS prop plane, he knew he had found a significant methane leak. His gas-detecting Picarro analyzer indicated he was flying through a plume of gas escaping at 900kg per hour. The colorless, odorless gas was enough to cover a football field to a height of 20 feet in a single day. But this flight wasn’t over the highly publicized Aliso Canyon in Los Angeles; Conley was circling the Bakken Shale, a rock formation in western North Dakota that has been aggressively pumped for oil and natural gas. Day in and day out, small leaks in oil and gas